Hot galvanizing process and apparatus

ABSTRACT

Apparatus is provided for continuously forming and galvanizing tubing that includes washing and acid pickling assemblies, a zinc manifold through which the heated tube moves for application of the zinc coating, and an air wipe and water quench assembly for treatment of the zinc coating. The washing and acid pickling assemblies include two concentric pipe sections joined and sealed adjacent their ends with the tubing being axially drawn through the assembly, the pipe section of smaller diameter having annularly and longitudinally spaced holes therein through which water or acid under pressure is counterconcurrently directed against the tube from the larger pipe section or header, thereby to prepare the entire outer surface of the tubing for galvanization. The zinc manifold has a central coating chamber in fluid communication with a heated zinc reservoir, and the molten zinc contained therein is pumped to such central chamber of the manifold at a rate substantially to fill same, with drains being provided in the manifold to recycle excess zinc to the reservoir and to establish zinc flow through such central chamber. The air wipe, positioned downstream of the zinc manifold, is operative to direct a helical countercurrent air stream against the periphery of the coated tubing to remove and redistribute excess molten zinc, such air wipe being positioned immediately upstream of a water quench trough operative countercurrently to cycle water at preselected temperature ranges and flow rates along the coated tubing. The process of the invention includes the steps of continuously advancing the tubing, heating such tubing, coating the surface of the tubing, wiping the coated tubing, and immediately water quenching the coated tubing, such steps being performed at interrelated and preselected temperatures and rates for controlling iron-zinc alloy thickness and coating thickness and appearance.

llnited States Patent 1 1 Rossi et al.

[ HOT GALVANIZING PROCESS AND APPARATUS [75] Inventors: Joseph R. Rossi, Cortland; Frederick J. Griffiths, Warren, both of Ohio; James L. Griffin, Jackson Center, Pa.; Gormen C. Palleson, Naperville, Ill. [73] Assignee: Maneely-Illinois Inc., Chicago, Ill. [22] Filed: Apr. 28, 1972 [21] Appl. No.: 248,739

[52] US. Cl 29/430, 29/200 B, 117/51,

117/114 A, 117/119.4, 266/3 R, 29/4777 [51] Int. Cl 1323p ll/00 [58] Field of Search 29/428, 430, 200 R, 200 B, 29/477.7; 117/51, 94, 114 R, 114 A, 119.4; 266/3 R, 4 R; 113/1 M, 116 UT [56] References Cited 9 UNITED STATES PATENTS 1,946,766 2/1934 Shonkwiler et al. 117/51 2,372,599 3/1945 Nachtman 204/206 2,424,034 7/1947 Hopper 1 266/3 R 2,926,103 2/1960 Brick 117/51 2,977,914 4/1961 Gray et al. 29/477.7 3,227,577 l/1966 Baessler ll7/ll9.4 3,230,615 1/1966 Krengel et a1... 29/200 B 3,256,592 6/1966 Krengel et al... 29/200 B 3,533,761 10/1970 Pierson 117/62 3,559,280 2/1971 Mailhiot et al..... 29/200 B 3,590,622 7/1971 Elge 29/477.7 3,620,805 ll/l97l Martin 117/51 3,716,908 2/1973 Rowell 29/477.7 3,727,895 4/1973 Wondergem ll7/ll9.4 3,736,174 5/1973 Moyer 117/114 B 3,768,145 10/1973 Ostrowski 29/477 7 FOREIGN PATENTS OR APPLICATIONS 889,790 2/1962 Great Britain 117/114 A 1,183,975 3/1970 Great Britain 117/114 A Nov. 5, 1974 PFzIhary Emmm rl w s tant Examinpr l 'hn r ru. Attorney, Agent, or F1rm-Donnelly, Maky, Renncr &

Otto

galvanizing tubing that includes washing and acid pickling assemblies, a zinc manifold through which the heated tube moves for application of the zinc coating, and an air wipe and water quench assembly for treatment of the zinc coating. The washing and acid pickling assemblies include two concentric pipe sections joined and sealed adjacent their ends with the tubing being axially drawn through the assembly, the pipe section of smaller diameter having annularly and longitudinally spaced holes therein through which water or acid under pressure is counterconcurrently directed against the tube from the larger pipe section or header, thereby to prepare the entire outer surface of the tubing for galvanization. The zinc'manifold has a central coating chamber in fluid communication with a heated zinc reservoir, and the molten zinc contained therein is pumped to such central chamber of the manifold at a rate substantially to fill same, with drains being provided in the manifold to recycle excess zinc to the reservoir and to establish zinc flow through such central chamber. The air wipe, positioned downstream of the zinc manifold, is operative to direct a helical countercurrent air stream against the periphery of the coated tubing to remove and redistribute excess molten zinc, such air wipe being positioned immediately upstream of a water quench trough operative countercurrently to cycle water at preselected temperature ranges and flow rates along the coated tubing.

The process of the invention includes the steps of continuously advancing the tubing, heating such tubing, coating the surface of the tubing, wiping the coated tubing, and immediately water quenching the coated tubing, such steps being performed at interrelated and preselected temperatures and rates for controlling iron-zinc alloy thickness and coating thickness and appearance 8 Claims, 12 Drawing Figures BACKGROUND OF THE INVENTION The present invention relates as indicated to a continuous tube forming and galvanizing process and apparatus and, more particularly, to a spray manifold for surface application of fluid, to a zinc manifold for uniform application of the galvanized coating to the tube, and to an air wipe and water quenching assembly downstream of such zinc manifold for treatment of the coated tube.

Galvanized tubing cut to predetermined lengths is extensively used, for example, as electrical conduit. Any process for manufacturing such conduit must produce an end product that passes stringent operational tests or standards in order to gain entry into the market and successfully to compete. There are at least two basic processes for the manufacture of galvanized tubing lengths from strip steel stock that meet the above requirements.

The first method constitutes a batch process wherein the tubing is formed and cut into sections, and the sections are subsequently dipped into tanks electrically to deposit zinc on the surfaces thereof. This process is relatively slow in that a number of distinct arid noncontinuous steps must be performed, with the product formed thereby being comparatively expensive and possessing certain structural disadvantages.

The second method, that is the continuous tube forming and galvanizing process, generally consists of a one pass operation in which strip stock is formed into a tube, and such tube is linearly drawn through both surface preparation operations and a molten zinc trough wherein the galvanize coating is applied to the peripheral surface of the tubing. Thereafter, the tubing is water quenched or otherwise cooled and then cut into predetermined lengths for subsequent use. The continuous tube forming and galvanizing method has several notable advantages over the batch process; namely, the entire operation is quickly performed, the inside surface of the tubing is free from molten zinc, andthe galvanize coating adheres well to the tubing under all operational tests.

Reference may be had to the Kringel et al U.S. Pat.

No. 3,122,] 14 for examples of the surface preparation and zinc application steps in a continuous tube forming and galvanizing process. The tubing is washed by axial passage through a plurality of spaced apart annular ring members in the form of headers having a plurality of spray nozzles arranged about the inner periphery for directing a spray onto the entire outer surface of the tubing. The pickling or acid preparation step is performed only along the longitudinal seam weld by two longitudinally extending, laterally spaced apart spray pipes arranged in the upper portion of the housing to overlie the tubing passing linearly therebelow, with the pipes each being provided with a number of spray nozzles positioned to direct the spray angularly downwardly to converge on such seam weld. It will thus be appreciated that the surface of the tubing is relatively well cleaned but only a portion of such surface adjacent the seam is pickled by a direct acid spray.

The zinc vat and zinc container disclosed in the above-noted Kringel patent are maintained under a non-oxidizing atmosphere by a large sealed cover, with the tubing continuously passing through a relatively shallow trough of zinc supported within the container.

The cover due to its size is difficult to remove thus preeluding quick access to either the trough or zinc vat. In

addition, each time the coveris removed the nonoxidizing atmosphere contained therein is lost and care must be taken properly to seal the cover upon repositioning the same in its sealing and enclosing position. The necessity of maintaining the nonoxidizing atmosphere and the disadvantages in maintenance and start up make the'utilization of the Kringel zinc bath less than desirable.

Accordingly, the principal object of the present invention is to provide a continuous tube forming and galvanizing process that uniformly produces a high quality galvanized tubing of controlled alloy and zinc layer thicknesses.

It is another important object of the present invention to provide fluid spray manifolds that direct such fluid against the tube passing axially therethrough in a direction countercurrent to tube movement. By concentrically arranging two pipe sections and providing the inner section with a plurality of angularly inclined holes in its wall, the fluid may be directed against the tube surface around its entire periphery at preselected pressures. The movement of such fluid in the defined countercurrent direction has been found to be extremely efficient in performing the desired cleaning or pickling functions.

It is still another object of the present invention to provide a zinc application or coating system that includes a manifold substantially completely full of mo]- ten zinc through which the continuous tubing at an elevated temperature passes. The movement of the tubing through the manifold serves uniformly to coat the tubing with the desired zinc thickness, with the galvanized coating formed thereby being excellently adapted to all conduit applications. By maintaining the coating chamber of the zinc manifold substantially completely full, it is unnecessary to maintain such chamber under a non-oxidizing atmosphere and access may readily be obtained to the central chamber without loss of either zinc or inert gas.

Yet another important object of the present invention is to provide an air wipe and water quenching assembly that is operative to remove excess zinc and control surface finish while uniformly depositing and freezing the remaining zinc to the tube periphery.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principle of the invention may be employed.

In the drawings:

FIGS. 1 and 1A are schematic flow diagrams of the continuous tube forming and galvanizing process in accordance with the present invention, the movement of the strip stock or tubing being indicated by the phantom lines and associated arrows;

FIG. 2 is a sectioned elevation of a single acid spray manifold assembly showing in fragment the continuous tube passing axially therethrough, with the arrow indicating tube travel direction and the broken lines showing the direction of acid spray against such tube;

FIG. 3 is a vertical section taken through the acid spray trough showing the arrangement of the spray manifold assembly in such trough, such section of the manifold assembly being taken along line 3-3 of FIG.

FIG. 4 is a fragmentary side elevation of the acid spray housing showing the assembly support saddle mounting block;

FIG. 5 is a fragmentary enlarged elevation of FIG. 1A showing the pre-heat and galvanizing sections of the process line,

FIG. 6 is an elevation of the galvanizing manifold showing the molten zinc reservoir in phantom lines therebelow, with portions of the manifold being broken away for ease of illustration;

FIG. 7 is an elevation showing the second guide roll stand with associated inert gas piping;

FIG. 8 is a fragmentary side elevation of the air wipe and water quench assembly;

FIG. 9 is a vertical section of the air wipe, with the coated tube being shown in fragment;

FIG. 10 is a fragmentary end elevation of the air wipe taken along line 10l0 of FIG. 9; and

FIG. 11 is a fragmentary plan view showing the introduction of inert gas into the tubing.

DETAILED DESCRIPTION OF THE PROCESS The important concepts of the present invention reside in the intermediate steps and apparatus (FIG. 1A) of the continuous tube forming and galvanizing process, but since such concepts were specifically conceived for and form an integral part of the overall process, the entire method will fundamentally be set forth with reference to FIGS. 1 and 1A before the details of the invention are described in context with the remaining figures.

Referring now to FIG. I, the tube forming mill is fed with strip steel 10 supplied in the form of coils l2 wrapped around pay-out reel 14, with such reel being mounted for free rotational movement on stand 15 to dispense strip steel as it is required by the continuous tube forming and galvanizing mill. The strip steel used is preferably 1010 or 1020 in grade designation, approximately 1.5 to 8 inches in width, and 0.042 to 0.065 inches in thickness. The strip stock is processed substantially continuously at a relatively constant rate through the mill, although the feed rate selectively may be varied in conjunction with other process variables to obtain desired tube characteristics. A feed rate for the strip stock and tube formed therefrom of from 300 to 400 fpm is preferred, but the mill is adapted to process the tubing at any rate between 50 and 400 fpm. Advancement may exclusively be effected by engagement between the strip steel and the forming, sizing and drive rolls rotating at relatively synchronized speed, whereby the strip steel is drawn into the mill for processing. In addition, pinch rollers may be used upstream of the tube forming mill to assist the latter in driving the strip as will be described in more detail below.

The strip stock carried by reel 14 is quickly exhausted at the above feed rate; accordingly, it is necessary to provide structure for accumulating and splicing the end of one coil with the leading end of another coil for joinder of the strips into a continuous length, without stoppage of the mill in its continuous operation. For

this purpose, a loop 16 is formed in the strip stock feed, such loop being of sufficient length continuously to pay-out strip steel to the mill while the trailing edge of the stock is held in a stationary position forjoinder with the leading edge of a new coil. The loop is formed by directing the strip stock alternately around individual members of two sets of elevated and horizontally spaced rollers 17 and I8.

Splicing of the coils is initiated by securing the strip of the first coil in clamp 19 with the trailing edge of such strip being held in welding machine 20. The leading edge of the second coil may then be brought into abutment with such other edge for joining the two coils by welding of the abutted edges, thereby to present a continuous strip length to the tube forming mill. During the splicing operation, the necessary lineal footage of strip stock for the process is provided by one of the roller sets, for example set 18, moving horizontally toward the other set as shown in phantom in FIG. 1, thereby to pay out strip 10 accumulated in loop 16. Upon completion of the splicing operation, the strip clamp 19 is released to allow the continuous strip stock to be drawn from coil 12, and the movable roller pair 18 is returned to the FIG. 1 position, thereby to reform loop 16 for the next splicing cycle.

The strip stock 10 is drawn from loop 16 along an elevated platform (not shown) and around two vertically offset rollers 21 and 22 into a strip wash mechanism 23. The strip wash mechanism serves to apply a washing agent, such as the synthetic mild detergent disclosed in Simborg US. Pat. No. 3,226,817, to both sides and the edges of the strip to clean and degrease the same for subsequent process steps. Such solution is preheated to a temperature between and F and is applied against the strip in a direction countercurrent to strip movement. Brushes 24 below and above the strip are rotated in a direction countercurrent to strip travel, such brushes being positioned so that the periphery of the same just contacts the surfaces of the strip. The strip then passes into a rinsing mechanism 25 of the same construction as washing mechanism 23 to apply preheated water to the strip in a direction countercurrent to strip travel. Conventional air wipes may be employed downstream of the brushes in each mechanism to remove the fluid applied.

The strip is drawn from the rinsing mechanism 25 by a pinch roll drive machine 26 having at least two laterally ofiset pairs of opposed rollers. Such pinch rollers add to the strip drawing power of the tube forming mill, thereby to remove some of the load on the latter. The drive mechanism 26 is provided with a dancer roller 27 operative to form a slack loop 28 in the line to provide sufficient strip to synchronize all downstream operations, the position of the dancer roll controlling the drive rate of the pinch rollers. Downstream of slack loop 28, the work is held in tension to insure uniformity in surface preparation and galvanizing steps.

The cleaned strip stock 10 then advances to a conventional tube forming roll section 32 wherein the strip is accurately bent to draw the edges of the same into abutting relationship. The formed tubing then moves through an electrode disc welder 34 which joins the two edges together. Seam shaving tools and wipers (not shown) may be employed after the weld is perfected to remove any external upset on the tubing, thereby to present a tube of substantially uniform cross-section to the remainder of the process line.

The terms tube and tubing as used herein are meant to encompass all endless cross sectional shapes into which a flat strip may be formed. Other shapes into which strip may be formed, such as Z bars and angles, may also be traversed through the process line.

After the tubing T has been welded, it is advanced to units operative sequentially to pickle and wash the outer surface of the formed tubing in preparation for continuous galvanizing. The pickling is performed in an acid spray machine 35 which includes three spray manifolds 40 and a divided acid reservoir 36. Such acid spray machine is described in more detail hereinafter with reference to FIGS. 2-4.

The surface rinsing step is performed by a water rinse directed against the tubing T by spray manifold 70, which may be substantially of the same configuration as the acid spray manifolds. The water rinse in manifold 70 serves to remove excess acid remaining on the tubing T after it passes through the acid spray machine 35.

As best shown in FIG. 5, the acid spray machine may be provided with a conventional air wipe 41 downstream of the manifold 40 for removing excess acid from the'tubing and drying the surface thereof. The water spray manifold likewise may be provided with an air wipe 71 for drying the tubing T after the water rinse.

After the tubing leaves the pickling and rinsing manifolds, it is important to maintain the surface thereof free from dirt accumulation or oxide formation to insure a good bond between the zinc coating and the steel tubing. The formation of an oxide layer on the tubing is particularly likely in view of the temperature to which such tubing is heated, unless protective measures are taken. Accordingly, the tubing T passes directly from the water rinse machine through a first guide roll stand 72 into a sealed inert gas manifold 73, the inert gas, as for example nitrogen, being effective to eliminate oxide formation on the external surface of the tubing. The tubing is maintained in a sealed inert atmosphere from manifold 73 through the zinc application step thereby to provide a surface for the zinc to adhere to that is free of surface oxides.

It will be appreciated that a certain amount of air is entrapped within the tubing upon formation, thus inherently allowing an oxide coating to be formed on the internal surface of the tubing as the temperature increases. However, the present invention includes, as shown in FIG. 11, the addition of inert gas by a jet 73av or the like just prior to tube welding, thereby substantially to have an inert gas encapsulated in the tubing to minimize the oxide formation on the internal surface thereof.

The tube T is then drawn axially through a second guide roll stand 74 into two linearly arranged and sealed insulating or shielding tubes 75 and 76, around which induction coils or heaters 77 and 78, respectively, are wrapped. A single shielding tube may be sub stituted for the two tubes if desired. The first induction heater 77 is designed primarily to remove latent moisture from the surface of the tubing and to begin heating the tube to the desired temperature. The second induction heater 78 completes the heating process with the tube reaching a temperature of from 300 to 1,300F. It has been found that temperatures at the lower end of the range may be preferred in order to produce a heavier, well adhered, zinc coating. For an example of a similar two stage induction heating unit with an intermediate inert gas drying jet, reference may be had to Beaudoin et al, US. Pat. No. 3,231,708. It will be appreciated, however, that a single induction coil or multiple coils may be used if desired.

The tubing advances from the induction heaters to a galvanizing manifold 80, wherein zinc is applied to the external surface of the tubing, as will be described in more detail with reference to FIGS. 4 and 5.

The tubing T is driven from the zinc manifold across an exposed portion of the zinc reservoir into the air wipe and water quenching apparatus, which is described hereinafter with reference to FIGS. 8 and 9. From the water quench, the galvanized tubing is traversed through a conventional sizer mill and straightening unit 108 and a cut-off shear I10. The lengths of galvanized conduit or tube are then processed along runoff equipment 112 to a double end facer, internal surface painting equipment, drying oven, cooling racks, inspection table, and marking and bundling benches.

DETAILED DESCRIPTION OF THE ACID AND WATER SPRAY MANIFOLDS Referring now in detail to FIGS. 2 and 3, tubing T is drawn axially through each of the three acid spray man ifolds 40 as indicated by arrow 41A. Each manifold assembly consists of two concentrically arranged pipe sections 42 and 43 of substantially equal length joined and sealed adjacent their ends. An acid resistant gasket 44 is employed between two flanges for sealing at one end while, at the other end, three wraps of acid resis- I tant packing 45 are compressibly positioned between annular sleeve 46, which is welded to pipe section 42, and flange 47.

The inner pipe section 42 is provided with a series of annularly and longitudinally spaced holes 50 in the wall thereof. The holes are inclined at an acute angle a of approximately 30 with respect to a horizontal plane so that the acid may be sprayed in the direction indicated by the dotted lines, that is in a direction countercurrent to the movement of the tube T. It has been found for best results that there should be nine, longitudinally spaced, annular groups of four holes each, with the holes in each group being both apart and rotated 22V2 with respect to similarly positioned holes in the immediately adjacent groups.

the trough positioning, associated piping, and operation of manifolds 40 are best described in conjunction with FIG. 3. Each of the manifolds 40 is mounted in the elongated acid spray housing 51 by longitudinally spaced support saddles 52 having arcuate top surfaces which cradle outer pipe section 43. Saddles 52 have laterally extending projections 53 which rest in longitudinally aligned notches 54 in opposed support blocks 55 mounted to the housing sidewalls. Such blocks 55 are provided with a second set of notches 56 of different depth than notches 54 so that the elevation of the spray assembly may be varied if needed in accordance with the diameter of the tubing being run.

The larger or outer pipe section 43 of the manifold is provided with a coupling 57 into which acid inlet pipe 58 is threaded. A heated acid solution comprising about 5 percent to 33 percent by volume hydrochloric acid dissolved in an aqueous medium is pumped through the inlet pipe 58 into the larger pipe or header 43 at approximately 47 psi. The acid solution is forced under the pumping pressure through holes 50 in pipe section 42 to impinge upon the external surface of tubing T moving axially therethrough, thereby to prepare the entire outer peripheral surface of the tubing for galvanization.

The larger pipe section 43 is additionally provided with two small drainage holes 59 in its bottom section adjacent both ends. Holes 59 serve as a drain outlet for acid remaining in pipe 43 during any shut-down of the unit. The excess acid either passing through drain holes 59 or escaping around tubing 36 at the inlet and outlet orifices of the assemblies accumulates in the bottom portion of housing 51. As best shown in FIG. 1, the bottom wall 60 of the housing is downwardly tapered at both ends to converge on intermediate flat section 61 which has two drain pipes 62 and 63 therein. Such drain pipes are positioned to lead to compartments 64A and 64B in the acid reservoir as formed by partition 65.

The three manifold spray assemblies 40 have a common acid supply header (not shown) from which the three fill pipes 58 branch to supply the large pipe sections 43 with an acid solution under pressure. The common manifold is in fluid communication with tanks 64 and 64A in acid reservoir 36, as best shown in FIG. 1A. The piping system (not shown) connecting the tanks 64A and 64B to the common acid header is operative to allow both tanks simultaneously to supply the manifold, to allow one tank to supply the manifold while the other tank is being cleaned and refilled, or to shut both tanks off from the manifold, thereby to discontinue operation. It will be appreciated that valves could be positioned in the three lead lines 58 to shut-off acid flow to any one or more of the manifolds 40, while the other manifolds remain operational. During such a selective shut-down, limited maintenance work could be performed on such manifold without discontinuing operation, although it is preferable to have the three acid spray manifolds simultaneously operating.

Drain pipes 62 and'63 are provided with acid resistant plugs 65, which are positioned in the inlet apertures of the same. As shown for example in FIG. 3, vertical operating rods 66 are connected at their lower ends to such plugs and extend upwardly through mov able cover 67 on housing 51. Handles, not shown, on rods 66 may selectively be pulled upwardly to unseat either plug 65. Such selection is made to unseat the plug above the acid compartment being used so that acid solution may be returned to the same. When the acid application cycle from a given compartment has been completed, the plug 65 may be reinserted in the drain pipe by pushing downwardly on corresponding handle 68 and the other plug 65 then removed.

The water spray manifold 70 may be constructed in the same manner as acid spray manifold 40, that is with two concentrically arranged pipe sections sealed and joined adjacent their ends. The inner pipe section of the water spray manifold is provided with annularly and longitudinally spaced one-sixteenth inch diameter holes, which are inclined at an angle of 30 with respect to a horizontal plane. The water inlet holes are arranged in four longitudinally spaced annular groups of four holes each, with the holes in each group being rotated 22 /a with respect to similarly positioned holes in immediately adjacent groups. A water rinse solution is pumped into the larger pipe section under a pressure between 10 and p.s.i., such rinse agent thereby being forced through the holes in the inner pipe section countercurrently against the outer surface of the tubing T moving axially therethrough. Therefore, the entire periphery of the tubing is rinsed in manifold and should be free of all excess acid applied to the tubing by acid spray manifolds 40. It will be understood that a drainage system for excess rinse solution, similar to that used for excess acid solution in the-acid spray machine, will be employed in the water rinse machine.

DETAILED DESCRIPTION OF THE GALVANIZING MANIFOLD Referring now to FIGS. 5 and 6, the galvanizing manifold consists of three different chambers, namely the entry vestibule 81, the main coating chamber 82, and the exit vestibule 83. The manifold is divided into the three chambers by two sets of transversely oriented flanges with suitable gasketing, as indicated generally at 84 and 85, each of such sets carrying an alloy flange 86 that is longitudinally and centrally oriented in the transverse set to provide apertures for the passage of the tubing. The orifices of flanges 86 are made of an alloy that is non-wetting in the presence of zinc, such as an alloy of molybdenum tungsten, and such orifices are of a diameter only slightly larger than the diameter of the tubing passing therethrough. The front wall 87 of the entry vestibule and the back wall 88 of the exit vestibules are provided with manifold inlet and outlet ports, respectively, which are in axial alignment with the apertures in flanges 86.

The central coating chamber 82 contains molten zinc that is heated in vat or reservoir 90 and then pumped to such chamber through inlet pipe 91. The zinc in the reservoir is heated by suitable heating means, such as gas fired burners, to a preselected fixed temperature above the melting point of the zinc coating. The zinc bath has suitable openings, such as in the top 92 thereof, for adding pigs of zinc to the reservoir in amounts corresponding to the zinc that is used or otherwise removed from the manifold. The level of the molten zinc in the reservoir 90 is thus maintained substantially at the level indicated by phantom lines at 93.

The molten zinc is pumped into chamber 82 at a rate sufficient to fill the substantially cylindrical housing 94 defining the major extent ofthe main chamber. The circular cross-section of the main chamber is interrupted and enlarged at two points along its length by rectangularly formed access frames 95 with hinged covers, such frames being of a width substantially equal to the diameter of housing 94 and a height slightly greater than the radius of such housing. The tops of drain pipes 96 are positioned in the additional space 97 about housing 94 created by access frames, such positioning permitting draining only after the pipe is completely full. The molten zinc pump is preset to maintain the coating chamber or cylindrical housing full, with any overflow returning to the zinc reservoir via drain pipes 96. The bottom of drain pipes 96 extend below the surface of the zinc 93 in vat 90, thereby to eliminate formation of zinc oxide in the zinc thus recycled.

It will likewise be appreciated that by maintaining the main coating chamber 82 substantially completely filled with the zinc it is unnecessary to maintain an inert or non-oxidizing atmosphere therein. The tubing T passing longitudinally through chamber 82 has its entire outer periphery coated with the molten zinc contained in such chamber. The temperature of the zinc in I chamber 82 is variably but precisely controlled by auxv iliary gas burners 99 so that the zinc bath temperature may be set according to process variables and the coating layer thicknesses desired. It will be appreciated that small quantities of a brightener, such as aluminum, may be added to the zinc either in the vat or in the coating chamber through the access frames.

Molten zinc may escape to the entry and exit vestibules from the main chamber 82 through the slight clearances between tube T and orifices in flanges 86. It is obvious that the cost of galvanizing tubing may be decreased by the expedient of recycling excess molten zinc to the reservoir not only from the main chamber, as described above, but also from the entry and exit vestibules. To this end, the side walls of the entry and exit vestibules extend below zinc surface 93, as shown at 100 and 101, respectively. By extending the bottom of the drain means below surface 93, the formation of zinc oxide is minimized which perpetuates the quality of the galvanize coating and eliminates clogging of inlet and outlet apertures 86 in the main chamber.

It has been found that even with an inert atmosphere in entry vestibule 81, a metallic dust is formed therein due to the overflow of zinc from the coating chamber. Such dust tends to move upstream in the process line toward the induction heating station and may begin to accumululate on the tube surface. To counteract such dust flow, inert gas is introduced into clearance 102 between tube T and shielding tubes 75, 76 for the induction heating coils. As best shown in FIG. 7, second guide roll stand 74 has three inert gas tubes 103-105 leading from a header 106 to clearance 102. The outlet ends of such tubes are peripherally spaced about such clearance and are bent in a horizontal orientation to direct inert gas down such shielding tubes. The downstream flow of such inert gas acts to retain the metallic dust in the entry vestibule eventually allowing such dust to settle into the zinc in vat 90. The dust backflow could also be precluded by baffling in the shielding tubes to block off clearance 102.

The galvanizing manifold 80 is designed for quick start up and maintenance due to the provision of a plurality of pivotal inspection covers. Such covers are positioned on the top of the entry and exit vestibules, as shown at 110 and 111, respectively, and on the top of the access frames 94 associated with the main chamber housing.

DETAILED DESCRIPTION OF AIR WIPE AND WATER QUENCH ASSEMBLY Referring now in more detail to FIGS. 8, 9 and 10, the air wipe and water quench assembly, indicated generally at 120, is positioned downstream of zinc manifold 80. Such assembly includes an air wipe 121 and water quench trough 160. The air wipe 121' is suspended from adjustment mechanism 122 mounted in cantilever position on support scaffold 123. Such scaffold is fixedly secured by suitable'fastening means 124 to table 125.

The adjustment mechanism 122 is adapted properly to orient the air wipe 121 with respect to the advancing coated tubingT. A first adjustment screw 126 with connected handle is operative on rotation to pivot the air wipe about a vertical axis for proper skew orientation with respect to the tubing T. Second screw 127 with connected handle is operative upon rotation to pivot air wipe 121 about a horizontal axis for skew orientation with tubing T. The remaining three screws 130432 with connected handles are operative upon rotation respectively vertically to adjust, laterally to traverse, and longitudinally to traverse the air wipe for positioning of the latter in the desired orientation with respect to the tubing.

As shown in FIG. 9, air'wipe 121 includes an outer or female member 135 having a stepped bore 136 decreasing in diameter from left to right as viewed in such figure. The left hand end of bore 136 is threaded as shown at 137 and the right hand reduced diameter end of the bore is undercut to form annular seat 138. Inner or male member 140 has an annular externally threaded projection 141 at its left end cooperatively to engage threads 127 of member concentrically to position the inner member within the outer member. Male member 140 is advanced into female member by turning until the forward or right end 141 of the same is received in seat 138 to seal the unit.

A tapered bore 142 extends through inner member with the leading edge of the same being annularly chamferred as shown at 144. The outer diameter of male member 140 and the inner diameter of female member 130 cooperate to define an annular chamber 145. An inlet duct 146 for a pressurized fluid, such as air, is welded to the external surface of female member 135, and the passage 147 in such duct communicates with elliptical opening 148 in female member 135. As best shown in FIG. 10, duct 146 is positioned tangentailly to direct the pressurized air into annular chamber 145.

The external surface of malemember 140 is inwardly recessed by oppositely configured, annular tapered surfaces 150 and 151 which take the form of truncated cones. The duct 146 is positioned adjacent left tapered surface 150 so that the air is tangentially introduced adjacent such surface and moves therefrom in a helical or spiral pattern toward the right tapered surface 151.

The front end 141 of male member 140 is provided with a plurality of inclined passages 154 extending between tapered surface 151 and internally chamferred surface 144. As best shown for example in FIG. 10, such passages 154 are longitudinally positioned to direct the air moving therethrough countercurrently against the peripheral surface of the tubing so that such air moves tangentially of the tubing rather than radially of the same. Therefore, pressurized air moves through chamber 145 in a spiral direction and then passes through passages 154 tangentially to engage the coated tubing. Such air movement results in a helical counter current air flow being directed peripherally along the tube T which initially results in redistributing the molten zinc on the tubing by taking excess portions collected at the bottom thereof and moving the same over the sides and top of the tubing. Such air movement action provides a uniform coating of desired weight and finished appearance. A wave front of zinc 156, as shown in FIG. 8, develops at the end of the effective air movement and the excess zinc at such point is backwardly and downwardly directed into zinc reservoir 90.

- The water trough for quenching the tubing T is positioned immediately downstream of air wipe 121.

' Such trough includes end walls having axially aligned tubing effectively to form a seal between such tubing and the end wall of the trough to preclude water emission from the outlet end.

The inlet end wall 161 of the trough has a forwardly extending nipple 162 mounted thereto, such nipple having a bore 163 complementary to and in registry with inlet aperture 164. The common diameter of the complementary nipple bore and inlet orifice is slightly larger than the diameter of the tubing T, such difference in diameters providing a clearance 166 for the water to pass from trough 160 in a direction countercurrent to the direction of tube travel. The nipple 162 has its forward end cut at a bias as shown in 170. Such bias cut has been found to have several advantages over an outlet opening positioned in a plane normal to tube travel; namely, such nipple allows more water to be put through the aperture, reduces water turbulence, presents a better wall of water against the entire tube periphery, and insures better coat uniformity.

It has been found that best quenching results are obtained by maintaining a given flow rate through nipple 162 at a temperature range of between 85 and 140F. To obtain such results, water is introduced into the downstream end of the trough, as shown at 167 in FIG. 1, and allowed to advance toward the inlet opening of the trough in a direction countercurrent to tube travel. The water during such movement passes in direct heat exchange relationship with the hot coated tubing, thereby to increase water temperature from trough inlet to outlet therefrom. A temperature sensor is positioned in nipple 162 to display the temperature of the water passing therethrough. lf the temperature begins to approach the upper limits of the acceptable range, additional water is inserted into the downstream end of trough 160. Such additional water has the effect of controlling the temperature of the water in the trough and results in bringing the temperature of the water passing through the nipple back to acceptable levels. The increased volume of water is bled off from the inlet end of the trough through suitable drain lines 168 so that the same volume of water continues to pass through the nipple. Therefore, when additional water is being added to the trough, valve 169 in drain line 168 is proportionately opened to drain volume of water from the trough equivalent to the volume of additional water added.

The water passing through the nipple is received in receptacle 170 which is turn communicates with secondary drain line 171. The water collected in drain line 168 and secondary drain line 171 is recycled for subsequent introduction into the downstream end of the water quench trough.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims, or the equivalent of such be employed.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method of continuously forming and galvanizing tubing comprising the steps of:

a. continuously feeding strip stock to a tube forming mill including the step of cleaning, degreasing and preparing at least the surface of the stock thus fed that is to form the outer surface of the tubing,

b. forming the stock so that the lateral edges thereof are in abutment;

c. welding the edges together to form the tubing;

d. spraying an acid solution against the entire outer periphery of the tubing in a direction countercurrent to the direction of tube movement;

e. wiping the tubing to remove excess acid;

f. rinsing the tubing to remove acid on the surface thereof by directing a rinse solution against the tubing in a direction countercurrent to tube movement;

g. wiping the tubing to remove the rinse solution;

h. preheating the tubing to a temperature between 300 and 1,300F while maintaining the tubing in an inert atmosphere;

i. applying molten zinc to the tubing by passage of the tubing through a chamber substantially completely filled with molten zinc;

j. wiping the tubing to redistribute the zinc on the tubing surface, to remove excess zinc, and to develop uniformity in coating thickness;

k. quenching the tubing to form a hardened zinc coating by immersing the tubing in water having a continuously maintained, controlled decreasing temperature gradient from tubing entry to the quench to tubing exit from the quench including the steps of sensing the temperature at the tubing entry and controlling the temperature of the water at tubing entry to a preselected range; and

l. cutting the continuous tubing into preselected lengths.

2. The method of claim 1, further comprising the step of introducing inert gas into the rolled stock just prior to seam welding.

3. The method of claim 1 wherein the quenching of the tubing to form a hardened zinc coating includes the step of immersing the moving tubing in water immediately following the step of wiping the tubing to preserve uniformity in thickness of zinc coat.

4. The method of claim 3 wherein the quenching of the tubing to form a hardened zinc coating includes the step of progressively cooling the tubing by moving the water in a direction countercurrent to tubing movement.

5. The method of claim 1 wherein the step of cleaning, degreasing and preparing the surface of the stock is performed before entry into the tube forming mill and includes brushing the stock surface to provide a textured surface on the stock.

6. A method of continuously forming and galvanizing strip stock comprising the steps of:

a. continuously feeding strip stock to a forming mill including the step of cleaning, degreasing and preparing the surfaces of the stock thus fed prior to entry into the mill;

b. forming the stock to a predetermined shape;

c. spraying an acid solution against the entire outer periphery of the formed stock in a direction countercurrent to the direction of stock movement;

(1. wiping the formed stock to remove excess acid;

e. rinsing the formed stock to remove acid on the surface thereof by directing a rinse solution against the formed stock in a direction countercurrent to tube movement;

f. wiping the formed stock to remove the rinse solution;

tween 300 and l,300F while maintaining the formed stock in an inert atmosphere;

h. applying molten zinc to the formed stock by passage of the same through a chamber substantially completely filled with molten zinc;

. wiping the formed stock to redistribute the zinc on the formed stock, to remove excess zinc, and to develop uniformity in coating thickness;

j. quenching the formed stock in water having a continuously maintained controlled temperature drop from stock inlet to the quench to stock outlet from the quench by continuously moving the water countercurrently to the direction of stock movement in a controlled flow rate to achieve a predetermined temperature range for the water at such stock inlet; and

k. cutting the continuously formed stock into preselected lengths.

7. The method of claim 1 wherein the temperature range at tubing entry to the water quench is between F and F.

8. The method of claim 1 wherein the water quench 

1. A method of continuously forming and galvanizing tubing comprising the steps of: a. continuously feeding strip stock to a tube forming mill including the step of cleaning, degreasing and preparing at least the surface of the stock thus fed that is to form the outer surface of the tubing, b. forming the stock so that the lateral edges thereof are in abutment; c. welding the edges together to form the tubing; d. spraying an acid solution against the entire outer periphery of the tubing in a direction countercurrent to the direction of tube movement; e. wiping the tubing to remove excess acid; f. rinsing the tubing to remove acid on the surface thereof by directing a rinse solution against the tubing in a direction countercurrent to tube movement; g. wiping the tubing to remove the rinse solution; h. preheating the tubing to a temperature between 300* and 1,300*F while maintaining the tubing in an inert atmosphere; i. applying molten zinc to the tubing by passage of the tubing through a chamber substantially completely filled with molten zinc; j. wiping the tubing to redistribute the zinc on the tubing surface, to remove excess zinc, and to develop uniformity in coating thickness; k. quenching the tubing to form a hardened zinc coating by immersing the tubing in water having a continuously maintained, controlled decreasing temperature gradient from tubing entry to the quench to tubing exit from the quench including the steps of sensing the temperature at the tubing entry and controlling the temperature of the water at tubing entry to a preselected range; and l. cutting the continuous tubing into preselected lengths.
 2. The method of claim 1, further comprising the step of introducing inert gas into the rolled stock just prior to seam welding.
 3. The method of claim 1 wherein the quenching of the tubing to form a hardened zinc coating includes the step of immersing the moving tubing in water immediately following the step of wiping the tubing to preserve uniformity in thickness of zinc coat.
 4. The method of claim 3 wherein the quenching of the tubing to form a hardened zinc coating includes the step of progressively cooling the tubing by moving the water in a direction countercurrent to tubing movement.
 5. The method of claim 1 wherein the step of cleaning, degreasing and preparing the surface of the stock is performed before entry into the tube forming mill and includes brushing the stock surface to provide a textured surface on the stock.
 6. A method of continuously forming and galvanizing strip stock comprising the steps of: a. continuously feeding strip stock to a forming mill including the step of cleaning, degreasing and preparing the surfaces of the stock thus fed prior to entry into the mill; b. forming the stock to a predetermined shape; c. spraying an acid solution against the entire outer periphery of the formed stock in a direction countercurrent to the direction of stock movement; d. wiping the formed stock to remove excess acid; e. rinsing the formed stock to remove acid on the surface thereof by directing a rinse solution against the formed stock in a direction countercurrent to tube movement; f. wiping tHe formed stock to remove the rinse solution; g. preheating the formed stock to a temperature between 300* and 1,300*F while maintaining the formed stock in an inert atmosphere; h. applying molten zinc to the formed stock by passage of the same through a chamber substantially completely filled with molten zinc; i. wiping the formed stock to redistribute the zinc on the formed stock, to remove excess zinc, and to develop uniformity in coating thickness; j. quenching the formed stock in water having a continuously maintained controlled temperature drop from stock inlet to the quench to stock outlet from the quench by continuously moving the water countercurrently to the direction of stock movement in a controlled flow rate to achieve a predetermined temperature range for the water at such stock inlet; and k. cutting the continuously formed stock into preselected lengths.
 7. The method of claim 1 wherein the temperature range at tubing entry to the water quench is between 85*F and 140*F.
 8. The method of claim 1 wherein the water quench step includes the further steps of passing the water along the tubing in a direction countercurrent to tubing flow and controlling the water flow rate in accordance with the sensed temperature of the water at such tubing entry to achieve the preselected water temperature range at such entry. 